1. Field of the Invention
The present invention relates to a zoom lens with a high zoom ratio, which is suitable for a single-lens reflex camera, compact camera, video camera, and the like and, more particularly, to a zoom lens with a high zoom ratio, which includes a wide field angle of about 80.degree. or more, and has a zoom ratio of about .times.4 or more.
2. Related Background Art
Conventionally, many zoom lenses each of which includes a wide field angle of about 70.degree. and has a zoom ratio of about .times.3 have been proposed. Each of such zoom lenses normally has a negative first lens unit, a positive second lens unit, a negative third lens unit, and a positive fourth lens unit. Since the negative lens unit is arranged at a position closest to the object side, a wide field angle is realized. In addition, the four-unit arrangement assures a high degree of freedom in aberration correction and increases the zoom ratio. As an example of such zoom lenses, Japanese Patent Application Laid-Open No. 62-63909 is known.
The field angle, at the wide-angle end, of the zoom lens proposed by Japanese Patent Application Laid-Open No. 62-63909 is about 70.degree., and the zoom ratio is about .times.3. However, in recent years, a zoom lens with a wider field angle and higher zoom ratio is required as a standard zoom lens for a single-lens reflex camera, and the zoom lens proposed by Japanese Patent Application Laid-Open No. 62-63909 cannot satisfy this requirement.
In order to satisfy the requirement associated with a wider field angle, Japanese Patent Application Laid-Open No. 5-173071 proposes a zoom lens including a wide field angle of 80.degree. or more. However, the zoom ratio of this zoom lens is as small as .times.2 or less, and this lens cannot satisfy the requirement associated with a higher zoom ratio.
On the other hand, in order to satisfy the requirement associated with a higher zoom ratio, Japanese Patent Application Laid-Open No. 5-313065 proposes a zoom lens having a zoom ratio exceeding .times.4. However, this zoom lens has a field angle, at the wide-angle end, of about 70.degree., and cannot sufficiently satisfy the requirement associated with a wider field angle.